filiberto.clara@LIGO.ORG - posted 13:02, Tuesday 18 February 2020 - last comment - 18:11, Tuesday 18 February 2020(55160)
ISC IO Chassis Powered Cycled /Baffle Photodiode Amplifier Powered On at EX
WP 8537
alog 55041
Ongoing noise hunting efforts at EX continue. Last week we moved auxiliary beckhoff electronics away from the ESD electronics (alog 55041) and powered down the Baffle Photodiode Amplifier chassis.
Today the ISC IO chassis 24V power was moved to same power supply that feeds the SEI IO chassis. Previously the 24V feeding the ISC chassis was also powering the slow controls Beckhoff electronics.
The Baffle Photodiode Amplifier chassis that was turned off last week was powered back on. Leaving unit off showed no change in our lines.
F. Clara, R. McCarthy
This afternoon Jenne and Camilla had a hard time taking care of green WFS at EX. Turns out that SEG1 of WFSB developed a huge offset of about -2000 counts after the IO chassis was power cycled, and that channel got much noisier too. This was not a sudden change. In the attached, the problem started at about t=-30000 (~ 17:30 UTC) and gradually got worse over the course of tens of minutes.
I was suspicious about analog problem, so I and Fil went to the end station and powered off WFS DC interface as well as AA chassis, but the offset remained. When Fil disconnected the AA chassis from the IO chassis, though, the offset jumped to ~-10k counts, WFSA SEG2 offset also jumped to -2k counts.
Next we power cycled the IO chassis anyway, and that particular problem went away. Don't ask me why.
Then we found, after driving back to the corner, that power cycling IO chassis, or maybe disconnecting AA from IO, triggered the safety system at EX to go crazy, the safety system thought that the status was fine but the laser interlock was kept open so the laser couldn't be turned on. This was manually bypassed.